This invention relates to a novel triphenylmethane polymer, an electrophotographic photoconductive composition and a member containing the triphenylmethane polymer.
Various photoconductive substances have heretofore been used in electrophotography. Of these photoconductive substances, organic photoconductive substances are particularly widely used. Typical examples of such photoconductive substances include triphenylamine-based compounds, triphenylmethane-based compounds, etc. For example, U.S. Pat. Nos. 3,542,544 and 3,542,547 disclose that such triphenylmethane-based compounds can be used as photoconductive compounds. These triphenylmethane-based compounds are incorporated in combination with sensitizing dyes into a binder such as polycarbonate and used. The leuco compound and the binder, such as polycarbonate, form an electric carrier transport layer, and the dye-aggregate forms an electric charge-producing layer.
Leuco compounds conventionally used, however, are somewhat soluble in petroleum solvents which are solvents for liquid developers. Therefore, they may migrate from the electric charge transfer layer, changing the construction and performance of the layer. This is a serious disadvantage which should be improved.
In order to employ the above described triphenylmethane-based compounds in the electrophoresis photographic process (PEP process), their leuco compounds were dispersed in polycarbonate to prepare the fine particles thereof, but the leuco compounds eluted in petroleum solvents used in the ink dispersion for electrophoresis. It has thus been confirmed that it is difficult to prepare an ink having a preferred composition from the triphenylmethane-based compounds and that it is not possible to employ the triphenylmethane-based compounds in the electrophoresis photographic process.
U.S. Pat. No. 3,660,083 also discloses that the leuco compound can be chemically bonded to the terminal of a polycarbonate oligomer to prevent the exudation of the leuco compound. A leuco compound so chemically bonded, however, is insufficient in the electric carrier transport ability, and, moreover, its preparation is complicated. It is, therefore, difficult to control the triphenylmethane structure content in the polymer, said triphenylmethane structure having the electric carrier transport ability.
As a result of extensive investigations to remove the above described defects of the heretofore known photoconductive substances, the inventors have succeeded in synthesizing a novel triphenylmethane polymer which has the structure resulting from polymerization of triphenylmethane and is a photoconductive polymer having excellent photoconductivity and other desirable characteristics.